An interior permanent magnet (IPM) machine is a brushless electric motor having permanent magnets embedded in its rotor core. Permanent magnet electric motors are reliable, light, and thermally efficient. In the past, however, permanent magnets have primarily been used on small, low-power electric motors, because of the relative difficulty associated with finding a material capable of retaining a high-strength magnetic field, and rare earth permanent magnet technology being in infancy.
Lower cost, high-intensity permanent magnets may be advantageous in an IPM machine. Compact, high-power permanent magnets may be useful in IPM machines for high-volume applications, such as for powering a vehicle, i.e. a hybrid or electric vehicle. IPM machines may be characterized by having favorable ratios of output torque versus the motor's physical size, as well as reduced input voltage. IPM machines may be reliable, in large part because permanent magnets are retained within dedicated slots of the machine's rotor. When supplied with motive energy from an external source, an IPM machine may also function as a generator. As a result, IPM machines may have a wide range of applications. For example, in the transportation industry, IPM machines may be used as powerplants for electric and hybrid electric vehicles. IPM machines may be used to move control surfaces, turn shafts and propellers, start engines, adjust seats and pedals, drive pumps, move machines, or any other application for motors or actuators.